1. Field of the Invention
The present invention relates to semiconductor modules, methods of manufacturing a semiconductor module, and mobile devices provided with the semiconductor module.
2. Description of the Related Art
Recently, with the trend toward miniaturization and high performance of electronic devices, there is a demand for reduction of the size of semiconductor modules used in electronic devices. To achieve this, narrow-gap electrodes for external connection of semiconductor components are essential. However, efforts for size reduction by narrowing the gap between electrodes have been successful only to a limited degree due to the constraints imposed by the size of solder balls and solder bridges produced. Recently, there are attempts to relocate the electrodes by routing lines (forming rewiring) in a semiconductor module in an effort to overcome the limitation. In one known method for relocation, a metal plate is half-etched so that a resultant bump (projection) is used as an electrode or a via, a semiconductor module is mounted on the metal plate via an insulating layer of, for example, epoxy resin, and the electrode for external connection of the semiconductor module is connected to the bump.
However, since copper (Cu) is generally used for a metal plate having a bump (and a wiring pattern in a semiconductor module having a bump), thermal stress is generated by the heat generated while the semiconductor module is in operation due to a difference in coefficient of thermal expansion between materials at an interface with the insulating layer. The thermal stress is concentrated in the bump projecting from and integral with a wiring pattern that extends parallel with the electrode of the semiconductor module. Therefore, disconnection may occur at an interface between the bump and the electrode. As efforts toward microfabrication of a bump itself are promoted for further miniaturization of a semiconductor module, the area of contact between the bump and the electrode will be reduced. Thus, there is a concern that disconnection may occur even more easily at an interface between the bump and the electrode due to the stress.
Since the metal plate (wiring pattern) and the insulating layer are adhesively attached to each other only at the contract surface, thermal stress may cause peeling so that reliability of the semiconductor module is lowered.